Superabsorbent crosslinked ampholytic ion pair copolymers

Abstract

The present invention provides an article of manufacture which contains a crosslinked ampolytic copolymer that is highly absorbent to aqueous electrolyte solutions. The articles of manufacture of the present invention contain copolymers formed by the copolymerization of an effective amount of each of the following components to produce a polymer which is highly absorbent to aqueous electrolyte solutions: (a) an ampholytic ion pair monomer comprising (i) the ammonium cation 3-methacrylamidopropyldimethylammonium and (ii) a sulfonate anion selected from the group consisting of 2-acrylamido-2-methylpropane sulfonate, 2-methacryloyloxyethane sulfonate, vinyl sulfonate, styrene sulfonate and combinations of two or more thereof; (b) at least one comonomer selected from the group consisting of acrylamide, methacrylamide, acrylonitrile, acrylic acid, methacrylic acid, alkali salts of acrylic acid, alkali salts of methacrylic acid, 3-methacrylamidopropyldimethylamine, 2-acrylamido-2-methylpropane sulfonic acid, alkali salts of 2-acrylamido-2-methylpropane sulfonic acid, 2-methacryloyloxyethane sulfonic acid, alkali salts of 2-methacryloyloxyethane sulfonic acid, N-vinyl-2-pyrrolidone and combinations of two or more thereof; and (c) at least one crosslinking agent which has at least two polymerizable olefinic functionalities wherein the olefinic functionalities are suitable for crosslinking. The invention also provides a method of using the polymers of the present invention for absorbing aqueous electrolyte solutions comprising the step of contacting the polymers of the present invention with the aqueous electrolyte solution.

We claim: 
     
       1. An article of manufacture selected from the group consisting of a paper towel and a disposable diaper containing therein a polymer formed by the copolymerization of an effective amount of each of the following components to produce a polymer which is highly absorbent to aqueous electrolyte solutions: (a) an ampholytic ion pair monomer comprising (i) an ammonium cation 3-methacrylamidopropyldimethylammonium and   (ii) a sulfonate anion selected from the group consisting of 2-acrylamido-2-methylpropane sulfonate, 2-methacryloyloxyethane sulfonate, vinyl sulfonate, styrene sulfonate and combinations of two or more thereof;     (b) at least one comonomer selected from the group consisting of acrylamide, methacrylamide, acrylonitrile, acrylic acid, methacrylic acid, alkali salts of acrylic acid, alkali salts of methacrylic acid, N-vinyl-2-pyrrolidone and combinations of two or more thereof; and   (c) at least one crosslinking agent which has at least two polymerizable olefinic functionalities wherein each of the olefinic functionalities is suitable for crosslinking.   
     
     
       2. An article of manufacture in accordance with claim 1 wherein the crosslinking agent is selected from the group consisting of N,N-diallylmethacrylamide, diallylamine, N,N-bisacrylamidoacetic acid, N,N'-bisacrylamidoacetic acid methylester, N,N'-methylenebisacrylamide N,N-benzylidenebisacrylamide, allylacrylate, diisopropenylbenzene, diallyl succinate, ethylene glycol diacrylate, diallylacrylamide, divinylbenzene, and combinations of two or more thereof. 
     
     
       3. An article of manufacture in accordance with claim 2 wherein the crosslinking agent comprises methylene-bis-acrylamide. 
     
     
       4. An article of manufacture in accordance with claim 1 wherein the polymer is at least partially hydrolyzed. 
     
     
       5. An article of manufacture in accordance with claim 1 wherein the polymer is at least partially neutralized. 
     
     
       6. An article of manufacture in accordance with claim 1 wherein the comonomer is selected from the group consisting of acrylamide, acrylonitrile, acrylic acid, alkali salts of acrylic acid, and any combination of two or more thereof. 
     
     
       7. An article of manufacture in accordance with claim 6 wherein the comonomer is acrylamide. 
     
     
       8. An article of manufacture in accordance with claim 7 wherein the polymer comprises a polymer formed by the polymerization of: (a) in the range of about 10 mole percent to about 30 mole percent of the ampholytic ion pair monomer;   (b) in the range of about 70 mole percent to about 90 mole percent of the comonomer, wherein the total amount of the ampholytic ion pair monomer and the comonomer equals 100 mole percent; and   (c) in the range of about 0.01 mole percent to about 0.3 mole percent of the crosslinking agent per 100 moles of the ampholytic ion pair monomer and the comonomer.   
     
     
       9. An article of manufacture in accordance with claim 8 wherein the polymer is formed by the polymerization of: (a) in the range of about 10 mole percent to about 25 mole percent of the ampholytic ion pair monomer;   (b) in the range of about 75 mole percent to about 90 mole percent of the comonomer, wherein the total amount of the ampholytic ion pair monomer and the comonomer equals 100 mole percent; and   (c) in the range of about 0.01 mole percent to about 0.2 mole percent of the crosslinking agent per 100 moles of the ampholytic ion pair monomer and the comonomer.   
     
     
       10. An article of manufacture in accordance with claim 7 wherein the sulfonate anion is selected from the group consisting of 2-acrylamido-2-methylpropane sulfonate and 2-methacryloyloxyethane sulfonate. 
     
     
       11. An article of manufacture in accordance with claim 10 wherein the polymer is formed by the polymerization of: (a) in the range of about 10 mole percent to about 30 mole percent of the ampholytic ion pair monomer;   (b) in the range of about 70 mole percent to about 90 mole percent of the comononer, wherein the total amount of the ampholytic ion pair monomer and the comonomer equals 100 mole percent; and   (c) in the range of about 0.01 mole percent to about 0.2 mole percent of the crosslinking agent per 100 moles of the ampholytic ion pair monomer and the comonomer.   
     
     
       12. An article of manufacture in accordance with claim 11 wherein the polymer is formed by the polymerization of: (a) in the range of about 10 mole percent to about 25 mole percent of the ampholytic ion pair monomer;   (b) in the range of about 75 mole percent to about 90 mole percent of the comonomer, wherein the total amount of the ampholytic ion pair monomer and the comonomer equals 100 mole percent; and   (c) in the range of about 0.01 mole percent to about 0.1 mole percent of the crosslinking agent per 100 moles of the ampholytic ion pair monomer and the comonomer.   
     
     
       13. An article of manufacture in accordance with claim 6 wherein the comonomer is acrylonitrile. 
     
     
       14. An article of manufacture in accordance with claim 13 wherein the polymer comprises a polymer formed by the polymerization of: (a) in the range of about 3 mole percent to about 35 mole percent of the ampholytic ion pair monomer;   (b) in the range of about 65 mole percent to about 97 mole percent of the comonomer, wherein the total amount of the ampholytic ion pair monomer and the comonomer equals 100 mole percent; and   (c) in the range of about 0.01 mole percent to about 0.3 mole percent of the crosslinking agent per 100 moles of the ampholytic ion pair monomer and the comonomer.   
     
     
       15. An article of manufacture in accordance with claim 14 wherein the polymer is formed by the polymerization of: (a) in the range of about 5 mole percent to about 25 mole percent of the ampholytic ion pair monomer;   (b) in the range of about 75 mole percent to about 95 mole percent of the comonomer, wherein the total amount of the ampholytic ion pair monomer and the comonomer equals 100 mole percent; and   (c) in the range of about 0.01 mole percent to about 0.2 mole percent of the crosslinking agent per 100 moles of the ampholytic ion pair monomer and the comonomer.   
     
     
       16. An article of manufacture in accordance with claim 13 wherein the sulfonate anion is selected from the group consisting of 2-acrylamido-2-methylpropane sulfonate and 2-methacryloyloxyethane sulfonate. 
     
     
       17. An article of manufacture in accordance with claim 16 wherein the polymer is formed by the polymerization of: (a) in the range of about 3 mole percent to about 35 mole percent of the ampholytic ion pair monomer;   (b) in the range of about 65 mole percent to about 97 mole percent of the comonomer, wherein the total amount of the ampholytic ion pair monomer and the comonomer equals 100 mole percent; and   (c) in the range of about 0.01 mole percent to about 0.2 mole percent of the crosslinking agent per 100 moles of the ampholytic ion pair monomer and the comonomer.   
     
     
       18. An article of manufacture in accordance with claim 17 wherein the polymer is formed by the polymerization of: (a) in the range of about 5 mole percent to about 25 mole percent of the ampholytic ion pair monomer;   (b) in the range of about 75 mole percent to about 95 mole percent of the comonomer, wherein the total amount of the ampholytic ion pair monomer and the comonomer equals 100 mole percent; and   (c) in the range of about 0.01 mole percent to about 0.1 mole percent of the crosslinking agent per 100 moles of the ampholytic ion pair monomer and the comonomer.   
     
     
       19. An article of manufacture in accordance with claim 6 wherein the comonomer is a alkali salt of acrylic acid. 
     
     
       20. An article of manufacture in accordance with claim 19 wherein the polymer comprises a polymer formed by the polymerization of: (a) in the range of about 1 mole percent to about 30 mole percent of the ampholytic ion pair monomer;   (b) in the range of about 70 mole percent to about 99 mole percent of the comonomer, wherein the total amount of the ampholytic ion pair monomer and the comonomer equals 100 mole percent; and   (c) in the range of about 0.01 mole percent to about 0.3 mole percent of the crosslinking agent per 100 moles of the ampholytic ion pair monomer and the comonomer.   
     
     
       21. An article of manufacture in accordance with claim 19 wherein the polymer is formed by the polymerization of: (a) in the range of about 1 mole percent to about 10 mole percent of the ampholytic ion pair monomer;   (b) in the range of about 90 mole percent to about 99 mole percent of the comonomer, wherein the total amount of the ampholytic ion pair monomer and the comonomer equals 100 mole percent; and   (c) in the range of about 0.01 mole percent to about 0.2 mole percent of the crosslinking agent per 100 moles of the ampholytic ion pair monomer and the comonomer.   
     
     
       22. An article of manufacture in accordance with claim 19 wherein the sulfonate anion is 2-acrylamido-2-methylpropane sulfonate. 
     
     
       23. An article of manufacture in accordance with claim 22 wherein the polymer is formed by the polymerization of: (a) in the range of about 1 mole percent to about 15 mole percent of the ampholytic ion pair monomer;   (b) in the range of about 85 mole percent to about 99 mole percent of the comonomer, wherein the total amount of the ampholytic ion pair monomer and the comonomer equals 100 mole percent; and   (c) in the range of about 0.01 mole percent to about 0.2 mole percent of the crosslinking agent per 100 moles of the ampholytic ion pair monomer and the comonomer.   
     
     
       24. An article of manufacture in accordance with claim 23 wherein the polymer is formed by the polymerization of: (a) in the range of from about 1 mole percent to about 10 mole percent of the ampholytic ion pair monomer;   (b) in the range of from about 90 mole percent to about 99 mole percent of the comonomer, wherein the total amount of the ampholytic ion pair monomer and the comonomer equals 100 mole percent; and   (c) in the range of about 0.01 mole percent to about 0.1 mole percent of the crosslinking agent per 100 moles of the ampholytic ion pair monomer and the comonomer.   
     
     
       25. An article of manufacture in accordance with claim 19 wherein the sulfonate anion is 2-methacryloyloxyethane sulfonate. 
     
     
       26. An article of manufacture in accordance with claim 25 wherein the polymer is formed by the polymerization of: (a) in the range of from about 1 mole percent to about 25 mole percent of the ampholytic ion pair monomer;   (b) in the range of from about 75 mole percent to about 99 mole percent of the comonomer, wherein the total amount of the ampholytic ion pair monomer and the comonomer equals 100 mole percent; and   (c) in the range of about 0.01 mole percent to about 0.2 mole percent of the crosslinking agent per 100 moles of the ampholytic ion pair monomer and the comonomer.   
     
     
       27. An article of manufacture in accordance with claim 26 wherein the polymer is formed by the polymerization of: (a) in the range of from about 1 mole percent to about 6 mole percent of the ampholytic ion pair monomer;   (b) in the range of from about 94 mole percent to about 99 mole percent of the comonomer, wherein the total amount of the ampholytic ion pair monomer and the comonomer equals 100 mole percent; and   (c) in the range of about 0.01 mole percent to about 0.1 mole percent of the crosslinking agent per 100 moles of the ampholytic ion pair monomer and the comonomer.   
     
     
       28. An article of manufacture in accordance with claim 6 wherein the comonomer is a combination of acrylamide and alkali salt of acrylic acid. 
     
     
       29. An article of manufacture in accordance with claim 28 wherein the polymer comprises a polymer formed by the polymerization of: (a) in the range of about 1 mole percent to about 20 mole percent of the ampholytic ion pair monomer;   (b) in the range of about 10 mole percent to about 25 mole percent of the acrylamide comonomer;   (c) in the range of about 55 mole percent to about 89 mole percent of the alkali salt of acrylic acid comonomer, wherein the total amount of the ampholytic ion pair monomer and the comonomer equals 100 mole percent; and   (d) in the range of about 0.01 mole percent to about 0.3 mole percent of the crosslinking agent per 100 moles of the ampholytic ion pair monomer and the comonomer.   
     
     
       30. An article of manufacture in accordance with claim 29 wherein the polymer is formed by the polymerization of: (a) in the range of about 1.5 mole percent to about 15 mole percent of the ampholytic ion pair monomer;   (b) in the range of about 10 mole percent to about 20 mole percent of the acrylamide comonomer;   (c) in the range of about 65 mole percent to about 88.5 mole percent of the alkali salt of acrylic acid comonomer, wherein the total amount of the ampholytic ion pair monomer and the comonomer equals 100 mole percent; and   (d) in the range of about 0.01 mole percent to about 0.2 mole percent of the crosslinking agent per 100 moles of the ampholytic ion pair monomer and the comonomer.   
     
     
       31. An article of manufacture in accordance with claim 28 wherein the sulfonate anion is selected from the group consisting of 2-acrylamido-2-methylpropane sulfonate and 2-methacryloyloxyethane sulfonate. 
     
     
       32. An article of manufacture in accordance with claim 31 wherein the polymer is formed by the polymerization of: (a) in the range of about 1.5 mole percent to about 15 mole percent of the ampholytic ion pair monomer;   (b) in the range of about 10 mole percent to about 21 mole percent of the acrylamide comonomer;   (c) in the range of about 64 mole percent to about 88.5 mole percent of the alkali salt of acrylic acid comonomer, wherein the total amount of the ampholytic ion pair monomer and the comonomer equals 100 mole percent; and   (d) in the range of about 0.01 mole percent to about 0.2 mole percent of the crosslinking agent per 100 moles of the ampholytic ion pair monomer and the comonomer.   
     
     
       33. An article of manufacture in accordance with claim 32 wherein the polymer is formed by the polymerization of: (a) in the range of about 6 mole percent to about 10 mole percent of the ampholytic ion pair monomer;   (b) in the range of about 10 mole percent to about 15 mole percent of the acrylamide comonomer;   (c) in the range of about 75 mole percent to about 84 mole percent of the alkali salt of acrylic acid comonomer, wherein the total amount of the ampholytic ion pair monomer and the comonomer equals 100 mole percent; and   (d) in the range of about 0.01 mole percent to about 0.1 mole percent of the crosslinking agent per 100 moles of the ampholytic ion pair monomer and the comonomer.